In the electrical network the power generated and consumption must always be in equilibrium. The extensive development of renewable energies means that sometimes there are significant overcapacities available. It is possible to manage the oversupply of controllable renewable energies in a number of ways; for example the fluctuating supply can be compensated for by increasing or reducing the capacity of conventional power plants, resulting renewable energy could not be fed into the network, in other words wind turbines could be deactivated, or the energy could be stored in an energy storage system, in other words in pumped storage power plants, compressed air storage power plants or batteries with high levels of system complexity and high costs in some instances.
EP 1 577 548 A1 and EP 1 577 549 A1 describe an apparatus and method for storing energy and generating power. A thermal storage unit is heated using electrical energy generated from renewable energies such wind or solar energy. The heat is used as required in the thermal storage unit to generate steam, which is fed directly to a thermodynamic process in a steam turbine, steam generation optionally being supplemented by conventional means.
U.S. Pat. No. 5,384,489 describes an apparatus in which electrical energy is generated by wind energy and used to operate a heating element to heat a fluid in a storage tank and an apparatus for extracting the stored energy from the tank again. The energy extracted from the storage tank is used for space heating/space cooling, general cooling and desalination but preferably for steam generation for generating electrical power.